Do noth­ing

While the rest of the pages of this mag­a­zine are all about the hard work put in by birds in find­ing food and sur­viv­ing day to day, here we look at one species that seem­ingly does not do much at all

Bird Watching (UK) - - Contents - Ref­er­ence: A Win­ter Roost of Grey Herons. T. R. Birk­head. Bri­tish Birds Vol 66, 4. 1973

Do­minic Couzens on the re­laxed life of the Grey Heron

If you would like to know what this ar­ti­cle is pri­mar­ily about, the an­swer is, well, noth­ing. Or at least, do­ing noth­ing. This is an as­pect of bird be­hav­iour that is very rarely writ­ten about. Since birds tend to be highly ac­tive crea­tures, seem­ingly al­ways fly­ing about or feed­ing or fight­ing, we some­times for­get that they do come to a halt some­times, and not just to sleep. At times in their lives birds just loaf, or lounge, or gaze at their navel (okay, they don’t have a navel) for hours on end. And this time isn’t merely in­ci­den­tal, but im­por­tant. One bird that lounges a lot is the Grey Heron. Much of the time, though, we don’t re­alise that it is do­ing it. Herons, as you know, are pa­tient fish-catch­ers, us­ing the act of stand­ing still as a for­ag­ing tech­nique, main­tain­ing po­si­tion pas­sively, hop­ing that a fish, or frog or small mam­mal will ap­pear at their feet. They will then reach down and grab it. How­ever, have you no­ticed how of­ten you see a heron by the wa­ter­side, per­haps on a log stick­ing out of the wa­ter, or on a high bank? Those are the mo­ments when we might say to our­selves: “How does it ex­pect to catch any­thing while stand­ing there?” Or you might see a group of Grey Herons, all in the same place, per­haps on an is­land in a lake, or in a damp field, stand­ing in stat­uesque pos­ture as if part of a sculp­ture park, and you as­sume they are all at least look­ing out for food. Those are the mo­ments they are em­phat­i­cally not do­ing any­thing of the sort. They are not for­ag­ing. They are do­ing noth­ing. Few birds stand idle in quite the way that Grey Herons do. They of­ten re­tract their neck and ap­pear to raise their shoul­ders, like a per­son caught in a down­pour lift­ing the col­lar of their rain­coat. They also as­sume a wild-eyed look that can ap­pear hi­lar­i­ously fed up, as if they were stuck in a queue at cus­tomer services. Of course, it is quite wrong to as­sume that they are fed up or an­gry. No­body knows what they are think­ing. How­ever, one thing might sur­prise you; for the most part they have cho­sen to be where they are. Day­time ‘roosts’ of Grey Herons have been stud­ied by, among oth­ers, the em­i­nent sci­en­tist Pro­fes­sor Tim Birk­head. He stud­ied a gath­er­ing of Grey Herons in a field in York­shire. The most remarkable of his re­sults is that many in­di­vid­ual herons spent al­most all the day­light hours sta­tioned there, do­ing noth­ing. There were asleep for only 6% of the time, and for nearly 77% of the day they sim­ply stood still, per­fectly awake. Some ar­rived shortly after first light and didn’t de­part un­til dusk. The ob­vi­ous ques­tion thrown up by this is: when did the birds keep them­selves alive by feed­ing? Al­though there is much in­di­vid­ual vari­a­tion, the an­swer is that they prin­ci­pally for­aged

at dawn and dusk. Al­most cer­tainly some hunted by night – who knows, per­haps by moon­light? How­ever, most herons are thought to roost by night (usu­ally in tall trees rather than on the ground), which leaves re­mark­ably lit­tle time to find food and a great deal of down time. How­ever, fish are highly nu­tri­tious and if a hunter strikes al­most im­me­di­ately, it is set up for the day. If a heron is able to catch its ideal-sized prey, which is around 15-20cm long, then it is per­fectly sa­ti­ated for hours after­wards. The same ap­plies to Cor­morants, which also spend in­or­di­nate amounts of time loaf­ing. This, at least, an­swers the ques­tion about herons be­ing fed up at their day­time roosts. Their stom­achs are full, so yes, they are lit­er­ally fed up! A heron sim­ply stand­ing still, then, is ac­tu­ally a con­tented heron, full of food, at a site of its choos­ing, safe if vig­i­lant. In con­trast to the time bud­gets of small birds, which some­times have to spend all the day­light hours in win­ter in­ces­santly for­ag­ing sim­ply to stay alive, the Grey Heron’s sched­ule is re­mark­ably re­laxed.

Heron ex­cep­tions

There are ex­cep­tions, of course. Not all in­di­vid­ual herons will find what they need so quickly and have the lux­ury of clear­ing their di­ary. First year herons, just a few months old, tend not to spend as long in day­time roosts as adults, sug­gest­ing that they spend more time for­ag­ing. Other stud­ies show that th­ese young­sters make more fre­quent for­ag­ing trips. Full adults tend to have their own ter­ri­to­ries, which they will de­fend, and soon be­come ex­pert in hunt­ing in fa­mil­iar sur­round­ings. They can choose the most prof­itable times and ex­act lo­ca­tions, based on their own pre­vi­ous ex­pe­ri­ence, and also en­sure that they are free from in­ter­fer­ence from young up­starts. Such birds dom­i­nate in what we might call the post-feed­ing roost. On the other hand, when the weather is par­tic­u­larly bad, with rain, wind and cold, no­body has it easy, so the day­time roost can be vir­tu­ally empty. Notwith­stand­ing their rel­a­tively set­tled sta­tion in life, there is one ac­tiv­ity that does ex­cite the in­ter­est of loaf­ing herons, and that is preen­ing. On the chilly York­shire field stud­ied by Birk­head, birds spent about 17% of their time work­ing on their plumage. That is nearly a fifth of their time at the day-roost, a per­cent­age of groom­ing time that nudges to­wards the strato­spheric lev­els seen in, for ex­am­ple, Love Is­land con­tes­tants. And on the sub­ject of preen­ing celebri­ties, herons also lay claim to an im­pres­sive, al­most Kylie Jen­ner-es­que range of hair/feather-care prod­ucts. High on this list is pow­der-down. This comes from paired groups of down feath­ers that oc­cur in dense patches on the breast, flanks and rump, and th­ese, in con­trast to other avian feath­ers, grow con­tin­u­ously. As they grow, how­ever, the ker­atin at the tip dis­in­te­grates, form­ing a very fine pow­der, with some par­ti­cles no big­ger than a mi­cron in thick­ness. This pow­der is wa­ter-re­sis­tant and has a con­sis­tency sim­i­lar to talc. The herons dis­trib­ute the pow­der-down around the body with the bill in the nor­mal preen­ing process. The pow­der mixes with grease and other im­pu­ri­ties on the plumage, mak­ing it co­ag­u­late into lumps that are easy to re­move. The other must-have preen­ing prod­uct is ef­fec­tively a spe­cialised comb. Herons can­not make it to Claire’s, so this ac­ces­sory has to be on their body. If you’ve ever seen a heron scratch­ing, that is the clue, be­cause the comb is on their feet or, more specif­i­cally, on the claw of their front mid­dle toe, their long­est. The lower edge is ser­rated or, to be tech­ni­cal, pecti­nated. If you com­bine the built-in comb with the ef­fects of pow­der-down, you have a very ef­fec­tive clean­ing sys­tem. How­ever, it does take time to keep the feath­ers in the best pos­si­ble con­di­tion. Many of us are fa­mil­iar with the sight of a heron stand­ing in a ‘bored’ pos­ture some dis­tance from the wa­ter. We of­ten as­sume that it is hav­ing an un­prof­itable time and would rather be some­where else. This, though, is quite wrong. Such as bird is more likely to be highly sat­is­fied and whiling away the hours with­out con­cern. So, as you can see, some­times it takes noth­ing to tell a story.

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